Projection video display devices such as a liquid crystal projector irradiate a display element such as a liquid crystal panel with light emitted from a light source such as a mercury lamp, and enlarges and projects a video formed by the display element with a projection lens onto a screen. The configuration of an optical system of the device includes an optical unit from irradiation with light emitted from the light source on the liquid crystal panel to formation of the video (hereinafter, referred to as an optical engine) and a projection optical system which enlarges and projects the video formed by the liquid crystal panel with a projection lens. In an optical engine of a color video display device, three liquid crystal panels for three primary colors (RGB) as display elements, a color separation system for irradiation light, and a color synthesis system for respective video colors are provided. Moreover, for adjusting a video-displaying position on the screen, a lens shifting mechanism which can move a projection lens in a direction perpendicular to an optical axis is provided in the projection optical system.
The lens shifting mechanism is arranged to move the projection lens in two directions perpendicular to the optical axis of projection light, i.e., a horizontal direction and a vertical direction, and is required to be reduced in size and have high accuracy. In Patent Literature 1, a structure is proposed which aims to downsize the lens shifting mechanism and improve the operability thereof and includes a manual operating portion, which is provided with an arrangement of operating knobs for horizontal direction and vertical direction, and a movement transmission mechanism portion for cutting off a transmitted force at a lens-shift-limit position by means of a clutch mechanism portion.